#include <iostream>

using namespace std;

int main()
{
	double n;
	scanf("%lf",&n);
	double r=10000,l=-10000;
	while(r-l>1e-8)
	{
		double mid=(r+l)/2;
		if(mid*mid*mid>=n) r=mid;
		else l=mid; 
	}
	printf("%.6lf",l);
	return 0;
}
